Process of making styrols



Patented Aug. 9, 1932 UNITED "STATES PATENT, OFFICE Om E. SMITH, O]? WES T ENGLEWOOD, NEW JERSEY, ASSIGNOB 1'0 THE NAUGATUCK CHEMICAL COMPANY, OF NAUGATUCK, CONNECTICUT, A CORPORATION OF CON- NEGTIGUEI.

rnocass or name S'LYBOLS No Drawing.

This invention relates to a process for' ried out in the presence ofinert gases, such.

- as nitrogen and carbon dioxide. The reac tion which takesplace during the cracking is reversible to a certain extent, depending upon the temperature, the concentration of the styrol in the reaction products and upon the presence of catalysts or catalytic material such as might constitute or form part of the reaction furnace. Hence, where the reaction is carried out with the alkyl benzol alone or in the presence of inert gases, there is a tendency for the hydrogen to recombine at least in part with the styrol and regencrate an alkyl benzol, with aconsequent reduction in the yield of styrol. Furthermore,

- other hydrocarbons are formed during the hydrogenation process and some of these en tocombine with the styrol. One byproduct which is formed during the cracking isbenzol. v r

Among the objects of the invention are to provide a method for increasing the yield of styrol or its homologues obtained by the pyrogenic dehydrogenation of ethyl or other alkyl benzols, to increase the concentrationof the sty 1-01 in the reaction products thus obtained, to carry out the dehydrogenation of the alkyl benzol in the presence of substances which favorably influence the reaction and minimize its reversibility, and toincrease both the productivity and efiiciency-of the rocess. A further object is to reduce the ormation of benzol as a by-product'in the process. a In carrying out the invention, benzol is mixed with an alkyl benzol, such as ethyl benzol and the mixture is then subjected to a cracking temperature in an ordinary form of cracking tube or furnace, but preferably there is also added to the mixture a. dehydro- Application and )r m a0, 1929. Berta! meuaasa.

genating compound or'mixture. It has already been found that certain materials when present during the reaction act chemically by combiningwith the hydrogen set free from the alkyl benzol to form substances whlch are stable under reaction conditions and thus prevent reversal of the reaction by which the hydrogen would recombinev with the styrol formed and regenerate an alkyl benzol. Some of the dehydrogenating compounds not only act chemically in this manner but they also release or form a gas which further assists the process -b reducin the partial pressure of the alkyl enzol.

cally to reduce the partial pr ssure of the alkyl benzol but have no chemic leifect. By

the use of a proper dehydrogenating com- .then subjected to cracking conditions, the

benzol favorabl affects the reaction by reducing the-partlal pressure of the ethyl benzol; As.before polnted out, one of the byproducts of the cracking of an alkyl benzol is benzol, and it apggars that by mixing benzol with the alkyl nzol prior to the crackin operation, the presence of this added benzo also minimizes the production of benzol as a by-product from the alkyl benzol and.

increases the production of styrol.

ther' materials are known which act only phy'si-' Among substances which act wholl or mainly chemically are carbon disulp ide,

carbon tetrachloride, ethylene and sulphur;

among those actingl wholly or largely physi- J90 cally are ethyl alco ol, acetone, nitrogen, ammonia and carbon dioxide; and amon those acting both chemicall and. phislica ly are ethylene chloride, sulp 'ur monoc oride, sulphur dichloride, sulphur dioxide. While in carrying of 213 benzol and benzol alone may be crack it is preferred, 'as' before stated, to

out the present invention a mixture carry out the cracking operation in the pres ence of material whlch acts chemically or' hemically and physically as well. This may the ingredients used, temperature measuring devices, theusual flow meters, pressure re be accomplished by mixing with the alkyl benzol and benzol one or more of the above substances. For instance, a combination of 100 parts ethyl benzol, 80 parts benzol, parts ethylene chloride and 4 parts sulphur,

has given excellent results, and almost equally good results have been obtained from a mixture of 100 parts ethyl benzol, 80 parts benzol, 15 parts acetone and 4 parts sulphur. In carrying out the process an iron or a chromel tube furnace may be used and it may be heated electrically or in any other suitable way. It should be provided with the usual accessory apparatus, such as containers for cording instruments, condensers, receivers,

' of ethyl benzol into thefurnace was approxetc. In the examples given in the present application,.anelectrically heated tube fur- .nace, either iron or chomel, 3 long and 4' inside diameter was used. The rate" of flow ir'nately 100 grams per hour for this size of tube. The temperature in the tube 'in the reaction zone may l'ie between about 600750".

C. and preferablybetween 675720 G.

The products of cracking were purified by a steam distillation followed by a fractionation using a four bulb pear column. 'When cracking ethyl benzol, the fraction distilling oif below 105 C. may be considered benzol; the fraction coming over 105 C. may be considered as a mixture of styrol and ethyl benzol. The proportion of styrol in the latter.

fraction is determined by heating a portion of the fraction in a sealed tube at 180 C.

.over night and recovering the'styrol resin so formed by steam distillation. The styrol resin is then dried and weighed. As showing the improved results obtained by adding benzol to the mixture before cracking, the following data is given using in one case a mixture of 100 parts ethyl benzol, 80 parts benzol, 15 parts ethylene chloride and 4 parts sulphur, this mixture being passed through a cracking tube and puri'fied as above described. There were obtained from the reaction products 31 parts styrol, 40 parts recovered ethyl benzol and 62 parts recovered benzol. The concentration of the styrol fraction was 44%, the productivity was 31% and the efficiency 51.7%. 4

Using-the same mixture but omitting the 80 parts benzol,. the recovery from the reaction-products was 27 .6'parts styrol, 37 parts recovered ethyl benzol and 1.5 parts recovered benzol. The concentration of the styrol fraction was 42.9%, the. productivity was 27.6% and the efliciency was44t%.

In the resent application, the term $pro ductivity is used to designate the ratio between the styrol produced and the ethyl ben-,

zol passed through \the cracking furnace. The term .efliciency is used to designate the ratio between the styrol produced and the ethyl benzol consumed during the dehydrogenation. The productivity, efliciency and concentration of styrol in the resulting steam distillate are all of importance for the best results with the process. Inert gases exert a favorable influence on eiiiciency but have only a moderate effect on productivityand concentration. On the other hand, the dehydrogenating compounds which react chemically readily give high concentrations of styrol. Dehydrogenating mixtures properly selected as'to ingredients and proportions so as to both reduce the partial pressure of the ethyl benzol and also chemically react, exert an extremely favorable influence on all three factors. When ethyl benzol is used as the starting material, the resulting material is ordinary styrol, .while when alkyl benzols are used containing one or more higher alkyl radicals in the side chain, various homologues of styrol are produced.

By mixing benzol with the alkyl benzol according 'to the present invention, the partial pressure of the alkyl benzol is reduced benzol and alkyl benzol to approximately 600 to 750 C. to thereby split the latter into a styrol and hydrogen, continuously reacting upon the hydro en with a material capable comprises heating a. preformed mixture'of of forming a sta le compound therewith under reaction conditions, and separating the styrol from the products.

2. The method of producing a styrol which comprises heating a preformed mixture of benzol and alkyl benzol to approxi mately 60O to 750 C. to thereby split the latter into a styrol and hydrogen while lowering the partial pressure of the alkylbenzol by the benzol, continuously reacting upon the hydrogen by a'material comprising sulphur and separating the styrol from the products.

3. The method of producing styrol which comprises heatin a preformedlmixture of benzol and ethyl benzol to about 600 to 750 C. in the presence of a material comprising sulphur, and separating styrol from the reaction'products.

4. The method of producing styrol which comprises. heating a preformed mixture of benzol and ethyl benzol to about 675'to 720 C. in the presence of sulphur and a volatile organic compound capable of reducing the partial pressure of the ethyl henzoi, an separating styrol from the reaction products. 1

5. The method of producing styrol which. comprises heating a, preformed ure of benzol and ethyl benzol to GOO-750 C. in the presence of a dehydrogenatin mixture comprising ethylene chloride an sulphur, and recovering styrol from the reaction products. Signed at Passaic, county of Passaic, State of New J e'rsey, this 17th day of April, 1929.

O H. SMITH 

